Why did you even marry your current wife? Get a divorce if you want to pursue this other woman, but keep in mind that even though the idea of a new relationship with someone else may sound like the right idea, it may not necessarily turn out to be great. I think you should focus your energy on bettering your own life, whether that means working on fixing your marriage, or working on pursuing a divorce; but clearly you have been avoiding taking care of yourself; and you've been neglecting your own needs for quite some time. You need to figure out how to improve your own life before you start flitting off with another woman.
"Caring is not an advantage."